This invention relates to the field of heavy duty continuous flow material processing equipment, more particularly continuous co-flow dryers for reducing the moisture content of slurries and similar materials. As used herein, "slurry" means a flowable or pumpable mixture of a liquid and one or more insoluble materials, typically with a high liquid-to-solid ratio. Most often the liquid is water. Examples of such slurries include meal processing such as meat, fish, or feather meal processing, soybean meal processing, and non-meal material processing such as ceramic slurry processing, and sewage or waste treatment processing. It is to be understood that the term "co-flow" refers to a design in which the air and material flow in the same direction in the dryer, in contrast to "counter-flow" designs, for example.
In the past, co-flow dryers were capable of drying slurries up to only about 60% moisture in a single pass without adding dry powder to the material to be dried.
The present air swept tubular dryer invention overcomes shortcomings of prior drying machinery, extending the range of slurries capable of being dried (in a single pass) up to about 90% moisture (or more), while continuing to provide the advantages of continuous flow drying, contrasting especially with rotary drum dryers and fluidized bed dryers which are typical of other continuous drying processes which differ from the process of the present invention in that there is typically very little mixing action in such processes. The air swept tubular dryer of the present invention has been observed to be more efficient and typically has much higher production rates of processing materials than do the rotary drum or fluidized bed type processes. For example, the present invention is capable of removing 750 pounds of water for every 1000 CFM of air used in the process, at production rates of up to 50 tons per hour of material processed, with a retention time in the dryer in the range of approximately 1/3 to 4 minutes.